Mutualistic relationships between male inflorescences of Elaeis guineensis Jacquin and its pollinator Elaeidobius kamerunicus Faust (Coleoptera: Curculionidae: Derelominae): Comparison between two cultivars for E. kamerunicus progeny emergence in North Sumatra Indonesia

Abstract

Elaeidobius kamerunicus completes its life cycle on male inflorescences while ensuring pollen transfer to female inflorescences. Over the past decades, oil palm breeding has prioritized yield potential over male inflorescence production. In young plantations, scare male inflorescences may result in insufficient pollen and breeding sites for E. kamerunicus, reducing or eliminating local populations. Consequently, reduced pollination lowers fruit set and yield. Our study assessed weevil emergence phenology and potential from 74 post-anthesis male inflorescences of two cultivars: 31 from a super-male and 43 from a high-yielding experimental cultivar. Male spikelet morphology was compared using field and laboratory data collected in North Sumatra in Indonesia (2020 -2022). Super-male palms had more spikelets (283 vs.174), greater total spikelet length (39 vs. 27 m) and higher E. kamerunicus emergence (17,500 vs. 13,100). The kinetic of emergence reveals that E. kamerunicus females emerged in a large number during 10 days and earlier than males which emerged during a longer period of time (18 days), indicative of protogyny in adult emergence. The predicted emergence kinetics indicate that E. kamerunicus from Experimental cultivar emerged earlier (1-2 days) than E. kamerunicus from Supermale and it also shows a difference in the timing of emergence between the two sexes. Thus, sex and cultivar jointly influence the emergence dynamics of E. kamerunicus. There was good evidence that the total length of the spikelets in an inflorescence positively influences the number of E. kamerunicus emergence events. We will discuss our results from the point of view of pollination.